| Objective In recent years, 200 thousand implants are used in our country every year. Annual growth rate remained at more than 20%, has a huge market potential and development space. However, at present, the number of doctors engaged in oral implant is still small, the level is uneven. Dental implants, as a medical technology that has a high demand for both operational accuracy and experience levels,any tiny errors in operation will affect the long-term functional and esthetic results, or even damage the mandibular nerve, maxillary sinus bottom and mucosa of nasal bottom and important anatomical structures, resulting in unnecessary complications. In addition, because oral space is narrow, and the barrier of buccal soft tissue, often unable to complete the surgery operation under direct vision, which will undoubtedly have a negative impact on the accuracy of planting. Through literature review, our research group found surgical robotics can resolve these problems. However, the existing surgical robot systems can't meet the needs of oral implant surgery, therefore, our team created an oral implant robotic system, to fill the gaps of this field. The system includes a host computer, a robot and a navigation system. The navigation system is robot's "eyes" for collecting the real-time space pose of the surgical area and the dental implant drill, which is mounted on the end of the robot arm. After the robot obtains these information, it can automatically track the surgical area during surgery, and automatically adjusts the dental implant drill's pose in the surgical area, according to the surgical plan to drill the implant hole precisely. Wherein the surgical navigation system collects the real-time pose of the surgical area and the drill,by tracking the special devices' tracing marker, which is mounted on the dentition and the drill. These special devices are spatial mapping devices. Not only the relative positional relationship can be determined between the surgical area and the drill, you can also set up the mapping between virtual space and real space surgery. Thereby converting positional relationship of the implant drill and surgical jaw between real space to virtual space, and through their 3D model showing the relationship in the display, in order to monitor the whole process of the implant surgery. However, there is no spatial mapping device can be used in our oral implant robot's navigation system, so in this research we decided to create a series of spatial mapping device, which can be used in our implant robot navigation system. And its application is studied in order to provide technical support for the precise operation of the robot.Materials and methods Part one: In order to simplify installation of the spatial mapping device, which is mounted on the dentition, we decide to use an impression of the dentition, which is made by oral silicone rubber impression material, to fix the spatial mapping device on the dentition. However, this approach requires a repositioning procedure, which is before surgery patient needs wear the spatial mapping device to scan CBCT,and then,after complete surgical planning, install the device on the dentition once again. If there is a big gap between the two positions, it will have an impact on the accuracy of navigation. So we first need to research the accuracy of the oral silicone rubber impression's reposition, in order to verify the feasibility of this approach. By comparing the distance of the silicone impression's twice position, which are on the dentition model to analyze the accuracy of silicone impression's repositioning. This distance is reflected by the tray's radiopaque markers, which are showed in the twice CBCT images. Take into account the time factor affecting the accuracy of the repositioning, we decide to research its long-term repositioning's accuracy. Further, in order to achieve precise measurement rapidly, needs to accurately and rapidly reconstructed 3D models of every part(radiopaque markers, dentition model and silicone impression),for the 3D reconstruction of CBCT images mainly through thresholding, the larger the difference of the adjacent gray scale value of the material, the more easily split and reconstruct their 3D models. But there are too many clinical materials can be chosen, especially silicone rubber impression material. Therefore we decide, first, by researching the differences of candidate materials' gray values in CBCT images, to choose the suitable experimental materials; then use the selected materials to research the immediate and long-term accuracy of silicone rubber impression's repositioning(5 each upper and lower cases, no excessive buccolingual and M-D undercut). Part two: With RE software design, 3D printing technology processing method, to design the spatial mapping device, which is mounted on the surgical area dentition. First of all, the research on the method of the tracer marker is optimized; second design its fixation device, and through reasonable design to enrich its function; last, use the 3D printer to make a set of the spatial mapping device, and research its assembly accuracy. Part there: In the same way as part two, create the spatial mapping device which is mounted on the implant dental drill. By studying the errors of bur's tip positions and errors of bur's axis between the actual assembly and design assembly, to quantitatively evaluate the accuracy of the assembly.Results and conclusions: 1. By comparing the vertical and horizontal comparison of the gray values of the CBCT images of candidate material, the optimal combination of the materials is obtained. Thay are DMG silicon rubber heavy-body as the silicone rubber impression material, Cavtion hydrophilic temporary restorative as a marker point materials, ultra anhydrite as the dental model material. The immediate accuracy of the silicone rubber impression material's repositioning was tested as below, on the upper dentition is 0.110±0.032 mm, on the lower dentition is 0.120 ±0.023 mm.These errors are less than the CBCT's voxel(0.25mm),so that them can be accepted. And verified that the accuracy of the silicone rubber impression material's repositioning was stable in 30 days, and it was not affected by the difference between the upper and lower teeth. The results show that this method can be used to fix the spatial mapping device on the teeth of the surgical area. 2. The best method of making the tracer marker was selected, and the high precision of tracer marker was made. A series of devices for fixing the spatial mapping device on the surgical area' teeth was successfully designed. The devices include two major categories for the upper jaw and the lower jaw, each of which comprises a large, medium and small 3 subcategories. Every subcategory includes 4 subtypes, namely for the missing anterior teeth type, bilateral posterior teeth loss type, right posterior teeth loss type and left posterior teeth loss type, and integrated mouth retainer, endoscope and suction socket on the interface. The spatial mapping error of the sample is 0.4115 ±0.1409 mm, which can meet the requirements of the robot system. 3. The spatial mapping device mounted on the dental implant drill was successfully created. The dental implant drill can be firmly installed on the end of manipulator. Its assembly accuracy as follows, the error of the bur's tip position about 0.3393 mm, the error of the bur's axis about 0.849°. The assembly accuracy has reached the expected research objective. |
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